Plug-in hybrid electric vehicles (PHEV's) have higher capacity batteries as compared to hybrid electric vehicles (HEV's) and primarily use electricity to power electric motors as their principal means of propulsion. For many PHEV drivers, the combustion engine is rarely operated, for instance, only when the battery state of charge (SOC) is almost exhausted. Unused fuel inside the fuel tank may degrade with age due to accumulation of acidity and waxing. Conventional PHEV fuel maintenance modes force the engine on after a certain fuel age is reached in order to consume all of the fuel inside the tank.
The inventors herein have recognized potential issues with the above approach. Namely, because fuel quality is not directly measured or determined, forcing the engine on after a certain fuel age is reached may prematurely consume undegraded fuel with unnecessary engine starts. For example, the degree of fuel degradation with time can depend on several factors such as the initial fuel quality, fuel type, engine age, and the like. Conversely, prior to reaching a certain fuel age, fuel degradation may be more severe than anticipated, and forcing the engine on in order to consume the severely aged and degraded fuel may cause unnecessary damage to the engine.
One approach which at least partially addresses the above issues includes a method, comprising on board a hybrid vehicle and executed by a vehicle controller on board the hybrid vehicle, determining a pH based on a pH sensor positioned in a fuel system; and in response to a first condition comprising the pH being less than a first threshold pH, disabling an electric motor and propelling the hybrid vehicle with an engine.
In another embodiment, a method for a hybrid vehicle having a controller may comprise providing the controller with executable instructions to: determine a fuel pH based on a fuel pH sensor; and execute a first fuel maintenance mode in response to the fuel pH being less than a first threshold pH for a first threshold time.
In another embodiment, a hybrid vehicle system may comprise: an engine; an electric motor; a fuel system; a pH sensor positioned in the fuel system; and a controller, with executable instructions to determine a fuel pH based on a fuel pH sensor, and execute a first fuel maintenance mode in response to the fuel pH being less than a first threshold pH for a first threshold time.
In this way, a technical result may be achieved in that prematurely consuming undegraded fuel and unnecessary fuel starts may be reduced. Furthermore, engine robustness may be increased because combustion of severely degraded fuel during engine operation can be reduced. Further still, reducing unnecessary fuel starts can increase fuel economy, and increasing engine robustness may reduce customer complaints. The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.